1. Field of the Invention
The present invention relates to a power connector for receiving an electric plug, and more particularly to a power connector provided with an improved safety shutter and preferably further provided with an improved Schuko grounding support system and/or an innovative power delivery architecture, allowing the invention to meet the strict international safety standards for household plugs, adapters and socket-outlets.
2. Description of Related Art
Each country has its own type of electric plugs and socket-outlets for specific current ratings, and the plug/socket types used in each country are normally regulated by national standards, many of which are listed in the International Electro-technical Commission (IEC) Technical Report, TR 60083. Among them, SASO/IEC60884-2-5 standards require that a plug or an adapter, after subjected to a one-hour overload test, the temperature rise should not exceed 45° K, while UL 498A further requires a maximum temperature rise of less than 30° C. when a device is carrying its maximum rated current. The strictness of the standards makes the traditional architectures almost impossible to comply therewith.
FIG. 13 shows a traditional adapter, which failed to pass the temperature rise test as described below. Without wishing to be bound by any theory, it is believed that the failure is attributed to the fact that the power frames 20″″ are indirectly connected to the plug pins 81″″ by placing a copper sheet 25″″ therebetween and pressing them together, resulting in loose contact and high resistance between the power frames 20″″ and the plug pins 81″″ and thus increasing heat generation.
Meanwhile, some European countries, including Portugal, Finland, Denmark, Norway and Sweden, require installment of safety shutters in socket outlets to prevent children from poking objects into them. To meet the requirement that the socket shutters can be opened up only when the live and neutral poles of a plug are inserted at the same time, some single-piece shutter designs have been proposed in the art, such as those disclosed in Great Britain Patent Publication Nos. 793000 and 2199996. However, such designs were frequently found hard to operate, as considerable force was needed to drive the relatively large shutter plate to its open position. It has also been found that the safety shutters of some conventional sockets will fail to work and the receiving surfaces of the safety shutters can wear out quickly, when receiving an electric plug with relatively sharp edges, such as a typical US polarized plug 9 having an edge inclined at 50° relative to its flat tip as shown in FIG. 6. The shortcomings are likely due to the small contact area between the plug tips and the safety shutters, as well as the relatively weak component force produced in the direction perpendicular to the insertion direction.
Additional problems may arise due to the limited space which the shutter plate must share with other elements in the socket cavity. For example, referring to the traditional universal socket arrangement illustrated in FIG. 13, an upright grounding system 50″″ is disposed at the center of the socket cavity and, thus, the shutter plate 30″″ is spatially hindered from moving towards the grounding system 50″″. To address this issue, the shutter plate 30″″ was arranged to open up the outlets by moving away from the grounding system 50″″. As a consequence, the traditional device is unsatisfactorily large in size and the portability thereof is undesirably compromised. Moreover, when a socket of this type receives a Schuko CEE 7/4 plug having flat grounding contacts, the safety shutters 30″″, biased by the spiral springs 33″″, apply a force to the live and neutral poles of the Schuko plug and, therefore, tend to push the plug away from the grounding metal of the socket to create a gap between the plug and the socket, causing a poor grounding connection. An unofficial test conducted by the inventors showed that the conventional safety shutters could disadvantageously lead to unreliable grounding connection at a defect rate as high as 40%.
Thus, there is a need for a power connector device that can fulfill the national safety requirements and address the shortcomings described above.